Bomb fuse



Sept. 17, 1946. E. c. MoRlARTY BOMB FUSE Fild April 2, 19:52

4 Sheets-Sheet 1 dtorrceg *Sept 17, 1946. E M0R|ARTY 2,407,844

BOMB FUSE Filed April 2, 1932 4 Sheets-Sheet 2 Sept. 17, 1946. E. c.MoRlARTY BOMB FUSE Filed April 2, 1932 4 Sheets-Sheet 3 Sepi 17, 1946-E. c. MoRlARTY l 2,407,844

BOMB FUSE Filed April 2, 1932 b4 Sheets-sheet 4 573 @JL M dfarmeyPatented Sept. 17, 1946 SITES. TENT OFFKC BOMB FUSE Ernest C. Moriarty,Washington, D. C.

Application April 2, 1932, Serial No. 602,795

10 claims. 1

This invcntion relates to bomb fuses and more particularly to fuses forbombs launched from aircraft.

The objects of this invention are:

First, to provide a bomb fuse that is simple in construction and is madeof few parts;

Second, to provide a bomb fuse Whose ring mechanism may be removed fromthe body of the fuse in either the armed or unarmed condition, Withoutremoving the body of the fuse from the bomb, and when so removed, allparts of the firing mechanism are self-contained and visible, and themechanism may be operated by hand;

Third, to provide a bomb fuse that has no loose part-s that might belost and whose firing mechanism, Which includes the initiating explosivetrain, may be stoWed separately from the body, Which may contain abooster charge;

Fourth, to provide a bomb fuse that may be armed or unarmed by handWithout removing any part from the fuse or the fuse from the bomb, andWithout the use of tools or spare parts. Also, fuses having been armedaccidentally may be returned to the unarmed condition Without the use oftools;

Fifth, to provide a fuse that can be readily checked as to completenessof assembly of its parts. their condition and ability to function;

Sixth, to provide a bomb fuse that has great resistance to firing Whenin the unarmed condition;

Seventh, to provide a bomb fuse that is more certain to fire byutilizing a plurality of initiating explosive trains;

Eighth, to provide means for obtaining various delays in arming of thefuse to suit the conditions under Which the bomb is to be launched;

Ninth, to provide a. bomb fuse that, if accidentally armed While beingcarried by an aircraft at high speed, will be automatically unarmed Whenthe speed of the aircraft is vreduced below a predetermined air speed;

Tenth, to provide a bomb fuse in Which the friction caused by the massof the parts is decreased as a function of the angle of inclination ofthe axis of the fuse With the horizontal;

Eleventh, to provide a bomb fuse that is relatively inexpensive tomanufacture and assemble.

With the above and other objects in view, this invention consists in thearrangement and construction of parts as Will be hereinafter more fullydescribed.

A bomb fuse usually consists of a firing mechanism that is designed toinitiate the exp-losion The large number of such fail-ures has resultedin the practise, especially in the larger size of bombs, of using twofuses in each bomb, one in the nose and one in Vthe tail of the bomb.Failure of a bomb fuse to function as intended may be due to defectiveelements in the detonating or ignition train, a defective booster, orthe defects in the firing mechanism, Which may be due to defects indesign or to the condition of the mechanism.

A bomb fuse is usually attached to'a bomb in an unarmed condition andremains so set until the bomb is launched on its flight. In its unarmedcondition a resistance is interposed to prevent the firing of theexplosive train leading to the main charge of the bomb, this resistancebeing sufiicient to prevent an accidental explosion or even permitting aheavy impact such as that caused by dropping the bomb on a hard surfacefrom any altitude less than that Which Will cause the explosion of themain charge of the bomb Without fuse action. Until a bomb is launched,its fuse usually is constrained from arming by a Wire or other suitablemeans. When launching a bomb, the' constraining Wire is removed and thefuse arms. As bombs are sometimes accidentally dropped While theaircraft is taking off and also because it is safer to use fuses that donot arm until the bombs have cleared the aircraft from Which they arelaunched, a delay in arming, after the constraining device is removed,is desirable,

A bomb fuse is in the armed condition When the resistance to firing issuch that the fuse Will function to explode the bomb when it impacts onan object or at the end of a time interval.

The resistance to firing in the unarmed condition' is usually obtainedby the physical strength of the parts of the mechanism, but it may beincreased by a discontinuity in the firing train of' the fuse. Such adiscontinuity is usually referred 'to as detonator out of line, and isaccomplished by anl arrangement Where the initi'ating explosive train isout of line With the fir- -i-ng pin and the lead to the booster and mainexplosive charge of the bomb When the fuse is unarmed. For a giveninitiating train of explosives there is a minimum distance that mustseparate it from the other explosives in order to insure that itsaccidental firing will not cause the detonation of the other explosivesin the bomb, the factor of safety increasing as the minimum distance isexceeded.

Bomb fuse; are usually armed by the action of air on a propeller, thetime required to actuate the propeller giving the desired delay. Thesize of a bomb fuse propeller is limited by the clearance in the bombracks. etc., and hence, the internal work due to friction, springs,etc., that is, to be overcome by the torque of the propeller is alsolimited.

This invention is based in part on the above consideration, and isapplicable to bomb fuses of the usual type of both nose and tail fuses,but is not limited thereto.

The mechanism of my invention is simple in construction and contains butcomparatively few parts. This is desirable. as it lessens the liabilityof malfunctioning due to the omission of parts or the use of defectiveparts during the assembling of the fuse. The mechanism may be assembledin two units; the fuse body, with or without a booster, and the firingmechanism: The firing mechanism may be removed from the fuse body withthe fuse in either the unarmed or armed condition, without removing thebody of the fuse from the bomb, and when so removed, all parts of themechanism are self-contained and visible and the mechanism may beoperated by hand. There are no loose parts that might be lost. Also, thefiring mechanism which includes the initiating explosive train may besto-wed separate from the body of the fuse which may oontain a weakercharge, a separate stowage of detonators being usually considered asafer practise. The fuses may be armed or unarmed by hand withoutremoving any part from the fuse or the fuse from the bomb and withoutthe use of tools or snare parts. Fuses that have been armed accidentallymay be returned to the armed condition without the use of tools. Theready means of checking the completness of the assembling of the partsof the fuse, their condition, and their ability to function, lessens theliability of malfunctioning of the fuses when the bombs are launched.

The resistance to firing when the fuses are in the unarmed condition isaccomplished by both physical strength of the parts of the mechanism andby the initiating ex'olosive trains being out of line with the firingpin and the lead to the booster charge. The construction and operationof the detonator holders is such that the detonator may be separatedfrom the booster lead by three or four times the distance usually foundin bomb fuses. In case of severe impact, a drop on a hard surface from ahigh altitude, resulting in crushing the parts of the fuse, anadditional safeguard is provided consistingr of means for sealing thelead to the booster. and thus increasing the resistance to firing inexcess of that due to the distance which separates the initiatingexplosive train from the lead to the lbooster charge.

The construction of the detonator holder is such that two o-r moreinitiating explosive trains may be mounted therein, and the fuse set tofire either one, as may be desired, or all may be fired simultaneously.The liability of malfunctioning due to a defective element in eithertrain is thereby reduced.

The delay in arming is accomplished by the action of an air operatedpropeller, the shaft of which looks the mechanism in the unarmed po- ILOsition and retains it in this position until the end of the delay. Thisis desirable as the resistance to firing is not lessened progressivelyduring the arrning delay, the other parts of the fuse remaining in theirunarmed position until the end of the delay, Means are provided forobtaining any length of delay that may be desired. In the case of divebombing, where bombs may be launched from a plane traveling in a nearlyvertical, vertical or beyond the vertical (plane on its back) direction,and where the velocity of the plane is practically equal to its terminalvelocity, all bomb fuses of the usual design arm too quickly. To meetthis condition, when there is a slow separation of the bomb and theplane (both falling practically in a vertical direction) means areprovided for obtaining a suitable delay by a relatively large number ofturns of a slow-revolving propeller having a steep pitch or theequivalent thereto.

In case a fuse should be accidentally armed when a bombl is carried byan aircraft traveling at a high speed, means are provided for unarmingthe fuse when the speed of the aircraft is reduced :below a given airspeed. This is desirable in case the aircraft is to land with bombsattached to it.

In the arming mechanisms of bomb fuses it is the usual practise to mountthe propellers so that they turn parts of the mechanisms on a screwthread, Due to the small torque developed by the propellers, generally afractional part of an inch-pound at an air speed of miles per hour,either the diameter of the screw threads or the mass of the revolvingparts must be relatively small. Bombs are generally carried in aposition practically parallel to the longitudinal axis of the aircraft,and are launched from this position. At low air speeds when the aircraftis traveling in a, direction which is substantially horizontal, thetorque, due to friction that must be overcome in order to turn a part ofthe fuse on a screw thread is practically proportional to the mass ofthe part and there is little if any change in the torque when the axisof the bomb is inclined to the horizontal. At high air speeds there maybe a thrust on the part due to the action of the air, especially if thepart is exposed to the air and the fuse is designed to operate at a lowterminal velocity. The difficulty experienced in turning parts of a fuseon a screw thread by the action of an air propeller is Well known tothose Skilled in the art, and their use in .bomb fuses has been limited.In order to overcome the difliculty of turning parts of considerablemass, I have devised means whereby the torque due to the friction causedby the mass of the parts is decreased as a function of the angle ofinclination of the axis of the fuse with the horizontal, so that theseparts may be operated by propellers of the usual size.

This invention may be best understood by reference to the accompanyingdrawings, in which:

Fig. 1 shows a fuse assembled in the nose of a bomb;

Fig. 2 shows a fuse asseinbled in the tail of a bomb;

Fig. 3 is a cross-section of the fuse in Fig. l showing the propellerafter it reaches the limit of its longitudinal travel and again after ithas rotated the striker somewhat;

Fig. 4 is a cross-section of the fuse on line fl-ll of Fig. 3;

Fig. 5 is a cross-section of the fuse on line 5-5 of Fig. 3;

Fig. 6 is a cross-section of the fuse on line 6-6 of Fig. 3;

Fig. 7 is a cross-section of the fuse on line 7-7 of Fig. 3;

Fig. 8 is a cross-section of Fig. 7 at 8-8;

Fig. 9 is a cross-section of the fuse on line 9--9 of Fig. 3;

Fig. 10 is a cross-section of the fuse on line li-l of Fig. 3;

Fig. 11 is a cross-section of the body of the fuse with the ringmechanism removed;

Fig. 12 is a plan view of the fuse body;

Fig. 13 is a cross-section of the firing mechanism removed from the bodyof the fuse;

Fig. 14 is a view of the firing mechanism from below;

Fig. 15 shows the fuse body 'in one piece;

Fig. 16 is a plan view of the fuse body in one piece;

Figs. 17 and 18 show the detonator holder with and without a pivot,respectively;

Fig. 19 is a view of the detonator holder from below;

Fig. 20 is a cross-section of a portion of the fuse through vent, firingpin, detonator and booster lead;

Fig. 21 shows a detent for holding the fuse in the armed position;

Fig. 22 is an elevation of the detonator holder showing the cam slot;

Fig. 23 shows how the fuse may be armed in three different positions;

Fig. 24 shows the detonator holder with three detonators;

Fig. 25 shows vthe firing pin holder with two ring pins;

Fig. 26 shows the detonator holder with two detonators;

Fig. 27 shows the firing pin holder with a skirt around the top;

Fig. 28 is a plan view of Fig. 27;

Fig. 29 is a diagram of the propeller having two vanes;

Fig. 30 shows a design with auxiliary vanes on the striker;

Fig. 31 shows a propeller with vanes set at two angles;

Figs. 32 and 33 show a spring that may be used for arming or unarming; I

Fig. 34 shows a looking pin for the fuse without a propeller;

Fig. 35 shows a striker with rollers to reduce the friction.

Similar numerals refer throughout the several views.

Reference numeral 59, Fig. 1, represents the body of a bomb, 3! the mainexplosive charge of a bomb, and 32 is a part of the booster chargeassembled in an adapter 33. Reference numeral 35 represents the body ofthe fuse, 36 a striker, 57 a propeller, 38 an arming wire that passesthrough a hole in 35 and through one vane of 37, it being retained inposition by a clip 39. Propeller 37 is secured to shaft 40 by nuts lil.The

to similar vparts axis of shaft is not coincident with the axis r of thebody of the fuse. Thumb screw 42 holds the firing mechanism in the fusebody 35.

In Fig. 2, 133 is the cone of the tail to which the vanesI 44 areattached. The body of the fuse is extended rearward and this extension,together with nut 45, serves as a means for holding the cone in place onthe bomb. The base of the cone 43 is secured to the bomb 35 by studs135, so that opening 4? is opposite thumb nut yllii. rE'he -cap 48covers the opening in the extension of the fuse 6 body. It does notrotate with the propeller shaft but with the striker to which it isattached. The clearance between the extension and cap must permitsufiicient longitudinal movement of the striker relative to the fusebody for the fuse to function.

In Fig. 3, @9 is the remainder of the booster charge assembled in thefuse body and held in place by a thin disk 50. Detonator holder 5| ispivoted on a small bearing surface in the body of the fuse by pivot 52and has a cylindrical stem 53 which projects through firing pin holder54 and is secured to striker 33 by a pin 55 that is shearable on impact.Firing pin holder 54 carries the ring pin, as will be described later,and is held in place -fby thumb nut 42. By unscrewing thumb nut 42, theentire firing mechanism can be lifted out of the body of the fuse. Thepropeller shaft di) is threaded throughout its entire length with theexception of the portion 56 which stops the rotation of the shaft whenit reaches bearing 57 which is internally threaded to cooperate with thethreads on shaft 40, and the 'propeller then turns the striker 36 anddetonator holder 5| to the armed position. Detonator holder 51 has asmall bearing surface 58 touching the firing pin holder 54. The realimportance of this will be explained later. The upper part of the fusebody 55 may be formed from a separate piece and forced onto the body 55as shown. Vent assures the easy passage of stem 53 into cavity 6! byallowing the enclosed air to escape readily.

Fig. 4 is a cross-section of the fuse at Fig. 3. This shows how pinsecures stem 53 to the cylindrical portion of striker 35. Threeprojections 62 extend from the top of the body of the fuse and haveintervening spaces. The height of these projections must be slightlygreater than the full movement required of the striker relative to thebody of the fuse in operation. Shaf-t ed passes through a slot that ispartly in the striker and partly in the fuse body and thus preventsrotation of the former relative to the latter until the shaft iswithdrawn during the arming of the fuse.

Fig. 5 is a cross-section of the fuse at 5--5, Fig. 3. This shows threeprojections 53 that extend from the lower` side of the striker 35, whichhas intervening spaces. In the unarmed condition of the fuse theprojections 53 are in alignmerit with the projections 62, therebypreventing longitudinal movement of the striker relative to the fusebody.

Fig. 6 is a cross-section of the fuse at 'e`-5, Fig. 3, but which isreduced from the dimensions of that figure. This shows the position ofthe detonator 64 in the detonator holder in the unarmed condition. Thisis shown in cross-section in Fig. 20.

Fig. 7 is a cross-section of the fuse at l Fig. 3, showing a vent hole55 that in the unarmed condition of the bomb is directly over thedetonator or initiating explosive train. This vent is for the escape ofgas in case the detonator should be fired accidentally when the fuse isunarmed. There is enough clearance around shaft fiil and striker 35 forthis gas to readily escape to the atmosphere. Piece 55 is the firing pinwhose position, as well as the location of the vent in firing pin holder5=t, is shown more clearly in Figs. 8 and 20. This pin is located at thesame radius from the axis of the fuse as the vent and diametricallyopposite it, so that the detonator, which is under the vent whenrotated. through Will be under the firing pin.

The method of supporting the firing pin by a small shearable pin isshown in Fig. 20. The end of thumb screw 42 enters a cavity in firingpin holder 54 and holds it secure in relation to the body of the fuse asthe striker and detonator holder rotate during the arming of the fuse.

Fig. 8 shows a portion of a cross-section of the fuse at 8-8, Fig. '7.The firing pin does not extend below the lower side, but does extendabove the upper side of ring pin holder 54 and to within a shortdistance from the cylindrical projection of striker 36. This, duringoperation, allows the firing pin sufiicient movement relative to thebearing 54 to insure explosion of the detonator.

Fig. 9 is a cross-section of the fuse at 9-6;

Fig. 3, but which is reduced from the dimensions of that gure. Thisshows the position of the lead '61 from the cavity of the fuse body topart of the booster charge 49. This lead 61 is in line with the firingpin as is shown in Fig. 20.

Fig. 10 is a cross-section of the fuse at ifl-lfl, Fig. 3. This showsthe method of obtaining an exact rotation of 180 of the striker anddetonator relative to the body of the fuse. Stop 68 is shown in theunarmed condition resting against one of the projections 62. During thearming operation, stop 66 passes through arcuate slot 66 and comes torest in cavity 16. Means for maintaining the stop in this cavity whilethe armed condition prevails, will be described later.

Fig. ll is a cross-section of the body of the fuse with the firingmechanism removed. Two of the projeotions 62 are shown here and thearcuate slot 69. Also, that part of the slot 86 contained in the fusebody, into which shaft 69 fits, is seen at the left of the cavity whichhormally holds the ring mechanism.

Fig. 13 shows the firing mechanism removed from the body of the fuse.and cavity 'il are in front of the plane of the section as shown inFigs. '7 and 9 respectively. The cavity 1.2 receives the end of thumbscrew 42.

Fig. 15 shows a fuse body of one piece, that is, part 59 is madeintegral with the body of the fuse instead of Sepa-rate as shown in Fig.3.

Figs. 17 and 13 show detonator holders with and without pivot 52.

Fig. 20 is a cross-section of a portion of the fuse through the vent,firing pin, detonator and booster lead. This shows the location of vent65 over the detonator 64 and firing pin 66 over cavity 16 in the unarmedcondition. She-arable pin '53 supports the firing pin until the strikershears it on impact. The lead 61, to part of the booster charge, isshown in line with the firing pin. Detonator 613 and lead 6? areretained in place by soft metal containers. Soft metal gasket M is forthe purpose of sealing lead 61 in case the bomb is accidentally droppedWithout arming. If the impact is sufiicient to shear projections 62 and63, Fig. 3, the striker will move longitudinally relative to the fusebody and impinges upon firing pin 56, shearing supporting pin '23,moving the firing pin into cavity 'H and forcing the detonator holderagainst gasket 'a'li whereby the lead 61 to the booster charge iseffectively sealed. It will thus be seen that there is a very highresistance to firing the main charge of the bomb by an impact on thestriker when the fuse is in the unarmed condition. In fact, it willstand any impact short of that sufiicient to fire the main chargewithout fuse action.

Fig. 21 shows a detent that, after the arming operation, will hold thefuse looked in the armed The firing pin 66 position until the bombstrikes its objective. The plunger 15 projects into cam slot 19 due tothe action of spring 16. Thumb nut 18 is for the purpose of withdrawingthe plunger from the cam slot in case it is desired to unarm the fuse byhand. Spring 15 acts on bushing 11 and a shoulder on plunger 15. Theplunger does not bear against the surface of the cam slot and thereforeoffers no initial moment, due to friction, that opposes the turning ofthe detonator holder in the fuse body. Such reduction of friction isimportant, as will be explained more fully later. However, during thearming operation, the cam slot has a large mechanical advantage incompressing spring 16, and when the slot is opposite the plunger, thecompressed spring will force the plunger into the slot and lock the fusein the armed condition. It will be seen that this gives an 180 movementof the detonator holder relative to the fuse body so that the firingpin, detonator and booster lead will be in line. The detent may also beapplied to the cylindrical projection of the striker and have the sameaction. Also, more than one detent may be used when the fuse is designedto be red with the detonator holder in several different positions, aswill be further explained later on.

Fig. 22 shows an elevation of a detonator holder showing the cam slot19.

Fig. 23 shows a slight change in design over that shown in Fig. 10whereby the fuse may be armed in three diiferent positions. Slots 69 arecut in two of the projections 62 and cavity'16 in the third one. Thefuse may be armed by stop 68, coming to rest against either of stop pins8| or cavity 16. The stop pins 8| may be inserted or removed, asnecessary. The amount of rotation of the firing mechanism relative tothe fuse body until the stop strikes the first stop pin is 60, thesecond stop pin 180 and the cavity 300.

This fuse has been shown with three projections 62, 63 on the body andthe striker, but it is evident that a fuse could be constructed with oneor two or more projections. If one projection on each part is used, thearming requires a rotation through an angle of 180', more or less,depending upon .the angles subtended by the projections. If twoprojections are used on each part, there will be two positions, one andone 270 from the unarmed position, in which it. may be arranged to havethe fuse armed.

Fig. 24 shows the detonator holder with three detonators so located thatone will be under the firing pin after a rotation of the firingmechanism relative to the fuse body of 60, 180 or 300 respectively. Eachdetonator consists of a percussion cap, a delay pellet and a detonatingelement. The delay pellets have different time delays so that aselection may be made of a delay suitable to the particular use to whichthe bomb is to be put.

Fig. 25 shows a firing pin holder 54 with two firing pins 66 and twovents 65 which in the unarmed position are over the two detonators shownin Fig. 26. Such an arrangement is desirable in order to decrease theprobability of failures.

Fig. 26 shows a detonator holder with two detonators 64. In the unarmedcondition the cavities 1| are under the respective firing pins 66 ofFig. 25, but a rotation of 180 of .the detonator holder relative to thefuse body will place the detonators under the respective firing pins ofFig. 25, so that on impact both detonators will be red simultaneously.

Fig. 27 shows a firing pin holder 54 with a skirt 82. Such anarrangement makes it possible to set the fuse deeper into the bomb withthe striker projecting from the bomb by as small a distance as may bedesired. The skirt is engaged by thumb screw 42 of Fig. 3 which, as isapparent, must be outside the bomb. The cylindrical portion of thestriker Fig. 13 is designed to project into the skirt of the firing pinholder to a point near the firing pin, in the unarmed condition, and tomove sufficiently far into the skirt to strike the firing pin andexplode the fuse on impact.

The distance that the striker of a nose fuse projects beyond the body ofthe fuse is largely determined by the angle from the vertical that it isdesired to have the striker impinge upon a horizontal surface, the angleincreasing as the projection of the striker from the body of the bomb isincreased.

Fig. 29 shows a diagram of a propeller having two vanes. If F representsthe resultant force acting on each vane, the torque about an axisperpendicular to the plane of the figure and passing through its centerwill be 2TF, r being the radius from the center of .the gure to thecenter of pressure of each vane. The torque about an axis parallel tothe above-mentioned axis but separated from it by a distance a: will be(r-x)F+(r+x)F=2rF. Hence, it follows that the torque about any axisparallel to the first mentioned axis will be 2rF.

Referring to Fig. 3, when the stop 56 of the propeller shaft reachesbearing 51, the torque of the propeller tends to turn the striker anddetonator holder about the axis of the fuse body. While .the propelleris turning, it stores up momentum and the moment of this momentum about.the axis of shaft 120 will be the same as that about the axis of thefuse. This can be readily proved by replacing the force in diagram ofFig. 29 by momentum.

Fig. 30 shows a modification in arming propellers that is desirablesometimes. Here auxiliary vanes 83 have been secured to the head of thestriker. With this design propeller shaft Lif) may or may not have thestop 56 as shown in Fig. 8. If the stop is omitted, the propeller screwsthe shaft out of the fuse and together they fall away from it in space.The striker is then rotated to the armed position by means of vanes 83.If the stop 58 is used, the striker is rotated by the combinedaction ofthe two propellers.

One of the major problems in designing fuses for bombs to be launchedfrom aircraft is the reduction of the internal friction of the fuseparts that must be overcome by the action of the propeller. In thepresent fuse, when the axis of the fuse is horizontal, the reaction, dueto mass of the striker on the body of the fuse, acts on the cylindricalprojection of the striker which extends into the fuse body. The radiusof the projection of the striker is relatively large and offers acorrespondingly large torque due to friction to be overcome by theaction of the propeller. After the bomb has been launched, the axis ofthe bomb and fuse turn towards the vertical. The reaction due to themass of the striker has two components, one acting on the projection ofthe striker and one on the small saring surface 53 of Fig. 3 which issupported by firing pin holder 543. When the fuse is Vertical, theentire mass of the striker and detonator holder is supported by bearing58. This bearing may be made as small as desired so that the torquenecessary to turn striker and detonator holder on this bearing when thefuse is Vertical will be less than the torque exerted by-the propeller.Transferring the reaction due to the mass of the parts to be turned froma bearing of large diameter to a bearing of small diameter when the axisof the fuse is inclined, results in a reduction of the moment due tofriction, and the reduction increases as the angle that the axis of thefuse makes with the horizontal increases.

When the fuse is used as a tail fuse, the reaction due to the mass ofthe striker and detonator holder is on the pivot 52 of Fig. 3, theaction of this pivot being similar to the small bearing 58 in the caseof a nose fuse.

When the terminal velocity of the striker of a nose fuse islconsiderably less than the terminal velocity of the bomb as a unit, thepivot 52 of Fig. 3 may be used to take the end thrust of the striker dueto the action of the air. When the terminal velocity of the striker ishigher than that of the bomb, the pivot 52 may be omitted as the strikerwill always tend to fall out of the bomb When its axis approaches thevertical.

In order to overcome the reaction of the shaft 49, Fig. 3, on bearing 51and the body of the fuse, a propeller having a maximum torque at zerovelocity of rotation is needed. Such propellers arm the fuse tooquickly. The propeller shown in Fig. 31 has been arranged to overcomethis fault. V When an air propeller with flat vanes is revolved by theaction of the air, the resultant direction of the air stream on thevanes changes so that the angle of incidence is reduced. If the load onthe propeller is small, the angle of incidence at the extreme radius ofthe vanes may be zero or less. In the latter case, the outward portionof the vanes acts as an air brake and the torque of this portion isnegative. When the torque due to the load on the propeller and thenegative torque equals the positive torque of the inner portion of thevanes, the corresponding velocity of rotation of the propeller will bethe maximum for that particular velocity and condition of the air.

In view of the above, vanes 84 of Fig. 31 are set to give the maximumtorque at zero velocity of rotation and vanes 85 are set normal to theair stream and hence give zero torque at zero velocity o f rotation ofthe propeller. But as the propeller turns, vanes 85 exert a negativetorque with the result that the maximum speed of the propeller under anygiven conditions is equivalent to that of a propeller having a verysteep pitch. Propellers made in this manner are very easy to adjust. Theproper size and shape of the positive vanes may be calculated and testedfor torque in a wind tunnel separately from vane 85, and when assembledin a propeller with vanes 85, the time for any number of revolutions maybe arrived at by adjusting the angle or size of the vanes 85, the timebeing shortened if they are inclined slightly so as to exert a positivetorque or being increased if they are inclined slightly in the oppositedirection. The two sets of vanes may be on one propeller or each set orcombination thereof may be contained in separate propellers mounted onone propeller shaft.

The operation of the propeller shafts is not limited to any particulartype of propeller, as any type giving sufficient torque and the desireddelay may be used. The propeller shafts may be shorter than those shownif the bombs are to be launched at low air speeds, but the' length mustbe suificient to engage the body of the fuse. With any given length ofpropeller'shaft, a preliminary adjustment may be made so that theportion entering the fuse is such as to give any desired delay less thanthe maximum delay that may be obtained for a given air speed andcondition of the air.

Figs. 32 and 33 show a further modification of the fuse. The spring 86is mounted on the core 81, one end of the spring being attached to piece88 which is soldered or otherwise secured to the core and, also,attached to the body of the fuse by pin 89. The other end of the springis attached to a slider 98 which has a projection 95 that may be turnedup or down. When turned up and inserted in a cavity in the striker, thespring will be compressed by rotation of the striker relative to thebody of the fuse. The movement of the slider is limited to 180 by thestop 93 which is formed by an increase in diameter of the core. Asshown, the spring opposes the action of the propeller to arm the fuse.The force exerted by the spring may be adjusted so that the fuse willnot arm until a given air speed is' exceeded, and if the fuse isaccidentally armed when the carrying plane goes into a steep dive, whereits air speed is high, it will unarm when the plane assumes normalflight and the air speed of the fuse is reduced below that for which thespring is adjusted. It is evident that the spring may be so arrangedthat it is elongated during arming by contracting returns the fuse tothe unarmed condition.

A spring may be designed to be in a compressed condition when the fuseis unarmed so that the force it exerts will assist in arming the fuse.Again, it may be designed to exert sufficient force to arm the fusewithout the action of a propeller, in which case the fuse may be lockedin the unarmed position by means of a pin 94, Fig. 34, which passesthrough the striker and a projection 95 on the body of the fuse, the pinbeing withdrawn by an arming wire 38 attached thereto. The springwithout a propeller gives a very quick arming arrangement, which may, ifdesired, have an initiating explosive train with a delay sufiicientlylong to allow the aircraft to reach a safe distance before the bombexplodes.

In case it is desired to have a fuse that arms very quickly when droppedfrom an aircraft traveling at a Very high speed at a low altitude, themoment due to the friction of the striker may be reduced by substitutingrollers 95 and 91, Fig. 35, for the projections 63 of Fig. 13. The viewof Fig. 35 is from below the striker. The rollers are supported bybearings 98 attached to the striker.

The rollers engage the inner surface of 59, Fig. 3, rolling thereon whenthe fuse arms. Rollers 96 do not touch the cylindrical portion of thestriker and rollers 97 do not touch each other.

It is evident that these rollers may be used in lieu of the projections53 of Fig. in any of the combinations of parts thatl have beenpreviously described.

The fuse may be designed to arm by a right or left-hand rotation of thestriker. When the direction of rotation is selected, the threads on thebase of the fuse should be such that the torque of the propellers doesnot tend to unscrew the fuse from the bomb.

It willV be understood that the above description and accompanyingdrawings comprehend only the general and preferred embodiments of myinvention, and that various changes in the construction, proportion andarrangement of 12 parts may be made within the scope of the appendedclaims without sacrificing any of the advantages of this invention.

I claim:

1. A bomb fuse comprising a fuse body having first projections withintervening spaces thereon and provided with a cavity therein, a strikerhaving second projections with intervening spaces thereon, a firing pinholder, a detonator holder, the three latter parts having a common axiswith said cavity, said firing pin holder being secured in the body ofthe f-use by means of a detent operated from without the body of thefuse, said detonator holder being at the bottom of the cavity and havinga stem passing through the firing pin holder and attached at the mouthof a cavity in said striker by a shearable connection, said strikerbeing mounted in the fuse body so that it may rotate between stops, saidfirst and second projections being in alignment in the unarmed conditionand being opposite corresponding spaces in the armed condition, a firingpin, a detonator, a lead to an explosive charge, the latter threeelements being out of line when the fuse is unarmed and being in linewhen the fuse is armed, a shaft for preventing rotation of the strikerand detonator holder relative to the fuse body when the fuse is unarmedand providing a delay during arming, and a propeller for arm- 1 ing saidfuse.

2. A bomb fuse comprising a fuse body having first projections Withintervening spaces thereon and provided with a cavity therein, a strikerhaving second projections with intervening spaces thereon, a firing pinholder, a detonator holder, the three latter parts having a common axiswith said cavity, said firing pin holder being secured in the body ofthe fuse by means of a detent operated from without the 'body of thefuse, said detonator holder being at the bottom of the cavity and havinga stem passing through the firing pin holder and attached at the mouthof a cavity in said striker by a shearable connection, said strikerbeing mounted in the fuse body so that it may rotate between stops, saidrst and second projections being in alignment in the unarmed conditionand being opposite corresponding spaces in the armed condition, a firingpin, a detonator, a lead to an explosive charge,

I" the latter three elements being out of line when the fuse is unarmedand being in line When the fuse is armed, a shaft for preventingrotation of the striker and detonator holder relative to the fuse bodywhen the fuse is unarmed and provid- 3 ing a delay during arming, a rstpropeller for removing said shaft from the fuse, and a second propellerattached to the striker for rotating the striker and detonator holderrelative to the fuse body to the armed position.

3. A bomb fuse comprising a fuse body having first projeotions withintervening spaces thereon and provided with a cavity therein, a strikerhaving second projections with intervening spaces thereon, a firing pinholder, a detonator holder,

the three latter parts having a common axis with said cavity, saidfiring pin holder being secured in the body of the fuse by means of adetent operatedV from without the body of the fuse, said detonatorholder being at the bottom of the cavity and'having a stem passingthrough the firing pin holder and attached at the mouth of a cavity insaid striker by a shearable connection, said striker being mounted inthe fuse body so that it may rotate between stops, said first and secondprojections being in alignment in the unarmed condition and beingopposite corresponding spaces in the armed condition, a firing pin, adetonator, a lead to an explosive charge, the latter three elementsbeing out of line When the fuse is unarmed and being in line when thefuse is armed, a shaft for preventing rotation of the striker anddetonator holder relative to the fuse body When the fuse is unarmed andproviding a delay during arming, a propeller for arming said fuse, and aspring for unarming said fuse at a predetermined air speed in case it isaccidentally armed.

4. A bomb fuse comprising a ifuse body having first projections Withintervening spaces thereon and provided With a cavity therein, a strikerhaving second projections With intervening spaces thereon, a ring pinholder, a detonator holder, the three latter parts having a common axisWith said cavity, said ring pin holder being secured in the body of thefuse by means of a detent operated from Without the body of the fuse,said detonator holder being at the bottom of the cavity and having astem passing through the ring pin holder and attached at the mouth of acavity in said striker by a shearable connection, said strikei` beingmounted in the fuse body so that it may rotate between stops, said firstand second projections being in alignment in the unarmed condition andbeing opposite corresponding spaces in the armed condition, a firingpin, a detonator, a lead to an explosive charge, the latter threeelements being out of line When the fuse is unarmed and in line When thefuse is armed, a pin for preventing rotation of the striker anddetonator holder relative to the fuse body before launching, a spring toarm said fuse after launching, and a detent to maintain the fuse in thearmed position.

5. A bomb fuse comprising a fuse body having first projections thereonWith intervening Spaces, a striker rotatably mounted in said fuse bodyand having second projections thereon with intervening spaces, saidsecond projections consisting of rollers that roll on an inside surfaceof a part of the fuse body and support the mass of the striker When theaxis of the fuse is horizontal, said first and second projections beingin alignment When the fuse is unarmed, and means for rotating saidstriker relative to said fuse body When the fuse is 14 being armed,whereby said first and second projections are opposite correspondingSpaces permitting longitudinal motion of said striker relative to saidfuse body.

6. A bom-b fuse comprising a fuse body having first projections thereonWith intervening spaces, a striker rotatably mounted in said fuse bodyand having second projections thereon With intervening spaces, saidfirst and second projections being in alignment When the fuse isunarmed, and means for rotating said striker relative to said fuse bodyWhen the fuse is being armed, Whereby said first and second projectionsare opposite corresponding spaces permitting longitudinal motion of saidstriker relative to said fuse body.

7. A bomb fuse comprising a striker, a detonator holder and meanscomprising a common axis about Which said striker and detonator holderturns While the fuse is being armed.

8. A bomb fuse comprising a. detonator holder, a plurality of detonatorscontained in said holder, a firing pin, a lead to an explosive charge,said detonators being out of line With said firing pin and said lead tothe explosive charge when the fuse is unarmed, and air pressureactuataible means for rotating said detonator holder relative to anduntil a preselected detonator is in alignment With said firing pin andlead to the `explosive charge.

9. A bomb fuse comprising a fuse body having first projections Withintervening spaces thereon, a striker having second projections withintervening spaces thereon, said first and second projections being inalignment When the fuse is unanmed but being opposite correspondingintervening spaces When the fuse is armed.

10. A bomb fuse comprising firing mechanism movable from an unarmedposition to an armed position and vice Versa, propeller means actuatableby air pressure to move said mechanism to the armed position, and meansenergized by said movement to the armed position effective to returnsaid mechanism to the unarmed position When the torque exerted by saidpropeller becomes less than a predetermined value.

ERNEST C. MORIARTY.

